The present disclosure relates to a signal potential converter for converting the potential of an input signal to pass a signal having a different potential.
As the feature size of transistors has been further reduced lately, their operating voltage has become lower and lower year after year. As for external interfaces, on the other hand, their operating voltage is rated in advance in accordance with a standard. Therefore, integrated circuits need to operate at an operating voltage of 5 V or 3.3 V, for example, so as to be connectible to existing devices as well. Thus, a level shifter (signal potential converter) is used to arbitrate between a signal to be driven by a micro-transistor and a signal to be driven at e.g., 5 V or 3.3 V. To transmit a signal at high speeds, in particular, an AC coupler using a capacitor may be used effectively.
PCT International Application Publication No. 2012/157031 discloses a configuration for reducing attenuation of a potential at a terminal node of a signal potential converter so as to prevent jitter from being produced in the converted signal.
Recently, there have been increasing demands for hybrid cores compatible with a plurality of interface standards. A single core may be required to operate sometimes at as high a rate as several gigabits per second (Gbps) and sometimes at a rate low enough to receive a burst signal representing data that does not change for a long time. If a signal potential converter such as the one disclosed in PCT International Application Publication No. 2012/157031 is used as such a core, the signal potential converter can certainly perform the high-speed operation. However, if the signal potential converter needs to operate at a low rate or receive a burst signal, the capacitor will be gradually discharged too much to maintain intended signal amplitude and always ensure normal operation.
Thus, the present disclosure provides a signal potential converter which may perform high-speed operation and which may still maintain intended signal amplitude and operate normally even while operating at a low rate or receiving a burst signal.